1. Field of the Invention
The present invention relates to a small disk cartridge in which a recording disk medium of diameter 50.8 mm (about 2 inches) or less is rotatably enclosed within a housing made up of a frame and upper and lower metal shells covering the top surface and bottom surface of the frame, and more particularly to the structure of the housing assembled.
2. Description of the Related Art
In mobile equipment such as a digital camera, etc., a very small disk cartridge, called “clik!™” such as that schematically shown in FIG. 9, is being used as a recording medium. This disk cartridge 1 is 50 mm in width, 55 mm in depth, and 1.95 mm in thickness. It has a housing, which is made up of a resin frame 2 and upper and lower metal shells (stainless steel sheets of 0.2 mm in thickness) 3, 4. The housing rotatably encloses a magnetic disk of diameter 1.8 inch (about 45.7 mm) which has a recording capacity of 40 MB, and is equipped with a U-shaped hole 6 through which a magnetic head is positioned over a recording surface of the magnetic disk, and a rotary shutter 7 that covers the U-shaped hole 6 when read and write operations are not performed. The upper and lower shells 3, 4 are laser welded at 10 or more positions (P) with the circumferential edges of the side walls engaged with each other.
In a magnetic disk cartridge (not shown) with a 3.5-inch (89-mm) floppy disk which is in wide use as a recording medium for personal computers, the upper and lower resin shells of the housing are assembled by ultrasonic bonding.
The structure of the assembled housing in the conventional disk cartridges described above, however, has the following problems: (1) an expensive, special machine such as a laser welding machine and an ultrasonic bonding machine is required and the upper and lower shells need to be precisely positioned so they are vertically aligned with each other; (2) paper or sputter dust occurs at the time of welding or bonding, adheres to a recording medium, and has an adverse influence on read and write operations, and also contaminates assembly space (which requires a class 100 to 1000 clean room); and (3) when disassembling the welded or bonded upper and lower shells for recycling or collection of classified refuse, the disassembly of them is fairly difficult and time-consuming, and since they are destroyed by disassembly, it is impossible to recycle them.